Configuring a Data Source in the Linux OS

Procedure

1. Obtain the source code package of unixODBC by following link:

   https://sourceforge.net/projects/unixodbc/files/unixODBC

   After the download, validate the integrity based on the integrity validation algorithm provided by the community.

2. Install unixODBC. It does not matter if unixODBC of another version has been installed.
   Currently, unixODBC-2.2.1 is not supported. For example, to install unixODBC-2.3.0, run the commands below. unixODBC is installed in the /usr/local directory by default. The data source file is generated in the /usr/local/etc directory, and the library file is generated in the /usr/local/lib directory.

   tar zxvf unixODBC-2.3.0.tar.gz
   cd unixODBC-2.3.0
   # Modify the configure file. (If it does not exist, modify the configure.ac file.) Find LIB_VERSION.
   # Change the value of LIB_VERSION to 1:0:0 to compile a *.so.1 dynamic library with the same dependency on psqlodbcw.so.
   vim configure
   
   ./configure --enable-gui=no #To perform compilation on an ARM server, add the configure parameter --build=aarch64-unknown-linux-gnu.
   make
   # The installation may require root permissions.
   make install

3. Replace the GaussDB client driver.

   Decompress the GaussDB-Kernel_VxxxRxxxCxx.x-xxxxx-64bit-Odbc.tar.gz package. After the decompression, the lib and odbc folders are generated. The odbc folder contains another lib folder. Copy all dynamic libraries in the /lib and /odbc/lib folders to the /usr/local/lib directory.

4. Configure a data source.
   1. Configure the ODBC driver file.

      Add the following content to the /usr/local/etc/odbcinst.ini file:

      [GaussMPP]
      Driver64=/usr/local/lib/psqlodbcw.so
      setup=/usr/local/lib/psqlodbcw.so

      For descriptions of the parameters in the odbcinst.ini file, see Table 1.

      Table 1 odbcinst.ini configuration parameters

      Parameter	Description	Example
      [DriverName]	Driver name, corresponding to Driver in DSN.	[DRIVER_N]
      Driver64	Path of the dynamic driver library.	Driver64=/usr/local/lib/psqlodbcw.so
      setup	Driver installation path, which is the same as the dynamic library path in Driver64.	setup=/usr/local/lib/psqlodbcw.so

   2. Configure the data source file.

      Add the following content to the /usr/local/etc/odbc.ini file:

      [MPPODBC]
      Driver=GaussMPP
      Servername=10.145.130.26 (IP address of the server where the database resides)
      Database=postgres  (database name)
      Username=omm  (database username)
      Password=    (user password of the database)
      Port=8000 (listening port of the database)
      Sslmode = allow

      For descriptions of the parameters in the odbc.ini file, see Table 2.

      Table 2 odbc.ini configuration parameters

      Parameter	Description	Example
      [DSN]	Data source name.	[MPPODBC]
      Driver	Driver name, corresponding to DriverName in odbcinst.ini.	Driver = DRIVER_N
      Servername	Server IP address. Multiple IP addresses can be configured.	Servername = 10.145.130.26
      Database	Name of the database to connect to.	Database = postgres
      Username	Database username.	Username = omm
      Password	Database user password.	Password= NOTE: After a user established a connection, the ODBC driver automatically clears their password stored in memory. However, if this parameter is configured, UnixODBC will cache data source files, which may cause the password to be stored in the memory for a long time. When you connect to an application, you are advised to send your password through an API instead of writing it in a data source configuration file. After the connection has been established, immediately clear the memory segment where your password is stored.
      Port	Port number of the server.	Port = 8000
      Sslmode	Whether to enable SSL.	Sslmode = allow
      Debug	If this parameter is set to 1, the mylog file of the PostgreSQL ODBC driver will be printed. The directory generated for storing logs is /tmp/. If this parameter is set to 0, no directory is generated.	Debug = 1
      UseServerSidePrepare	Whether to enable the extended query protocol for the database. The value can be 0 or 1. The default value is 1, indicating that the extended query protocol is enabled.	UseServerSidePrepare = 1
      UseBatchProtocol	Whether to enable the batch query protocol. If it is enabled, DML performance can be improved. The value can be 0 or 1. The default value is 1. If this parameter is set to 0, the batch query protocol is disabled (mainly for communication with earlier database versions). If this parameter is set to 1 and support_batch_bind is set to on, the batch query protocol is enabled.	UseBatchProtocol = 1
      ForExtensionConnector	This parameter specifies whether the savepoint is sent.	ForExtensionConnector = 1
      UnamedPrepStmtThreshold	Each time SQLFreeHandle is invoked to release statements, ODBC sends a Deallocate plan_name statement to the server. A large number of such statements exist in the service. To reduce the number of the statements to be sent, stmt->plan_name is left empty so that the database can identify them as unnamed statements. This parameter is added to control the threshold for unnamed statements.	UnamedPrepStmtThreshold = 100
      ConnectionExtraInfo	Whether to display the driver deployment path and process owner in the connection_info parameter mentioned in connection_info.	ConnectionExtraInfo = 1 NOTE: The default value is 0. If this parameter is set to 1, the ODBC driver reports the driver deployment path and process owner to the database and displays the information in the connection_info parameter (see connection_info). In this case, you can query the information from PG_STAT_ACTIVITY.
      BoolAsChar	If this parameter is set to Yes, the Boolean value is mapped to the SQL_CHAR type. If this parameter is not set, the value is mapped to the SQL_BIT type.	BoolsAsChar = Yes
      RowVersioning	When an attempt is made to update a row of data, setting this parameter to Yes allows the application to detect whether the data has been modified by other users.	RowVersioning = Yes
      ShowSystemTables	By default, the driver regards the system catalog as a common SQL table.	ShowSystemTables = Yes

      The valid values of Sslmode are as follows:

      Table 3 Sslmode options

      Sslmode	Whether SSL Encryption Is Enabled	Description
      disable	No	SSL connection is not enabled.
      allow	Possible	If the database server requires SSL connection, SSL connection can be enabled. However, authenticity of the database server will not be verified.
      prefer	Possible	If the database supports SSL connection, SSL connection is recommended. However, authenticity of the database server will not be verified.
      require	Yes	SSL connection is required and data is encrypted. However, authenticity of the database server will not be verified.
      verify-ca	Yes	SSL connection is required and whether the database has a trusted certificate will be verified.
      verify-full	Yes	SSL connection is required. In addition to the check scope specified by verify-ca, the system checks whether the name of the host where the database resides is the same as that on the certificate. GaussDB does not support this mode.

5. Configure the environment variables on the client.

   vim ~/.bashrc

   Add the following information to the configuration file:

   export LD_LIBRARY_PATH=/usr/local/lib/:$LD_LIBRARY_PATH
   export ODBCSYSINI=/usr/local/etc
   export ODBCINI=/usr/local/etc/odbc.ini

6. Run the following command to validate the addition:

   source ~/.bashrc

Verifying the Data Source Configuration

Run the ./isql -v MPPODBC command (MPPODBC is the data source name).

Troubleshooting

• [UnixODBC]connect to server failed: no such file or directory

  Possible causes:

  • An incorrect or unreachable database IP address or port was configured.

    Check the Servername and Port configuration items in data sources.

  • Server monitoring is improper.

    If Servername and Port are correctly configured, ensure the proper NIC and port are monitored based on the database server configurations in the procedure in this section.

  • Firewall and network gatekeeper settings are improper.

    Check firewall settings, and ensure that the database communication port is trusted.

    Check to ensure network gatekeeper settings are proper (if any).

• [unixODBC]The password-stored method is not supported.

  Possible causes:

  The sslmode configuration item is not configured in the data sources.

  Solution:

  Set the configuration item to allow or a higher level. For details, see Table 3.

• Server common name "xxxx" does not match host name "xxxxx"

  Possible causes:

  When verify-full is used for SSL encryption, the driver checks whether the host name in certificates is the same as the actual one.

  Solution:

  To solve this problem, use verify-ca to stop checking host names, or generate a set of CA certificates containing the actual host names.

• Driver's SQLAllocHandle on SQL_HANDLE_DBC failed

  Possible causes:

  The executable file (such as the isql tool of unixODBC) and the database driver (psqlodbcw.so) depend on different library versions of ODBC, such as libodbc.so.1 and libodbc.so.2. You can verify this problem by using the following method:

  ldd `which isql` | grep odbc
  ldd psqlodbcw.so | grep odbc

  If the suffix digits of the outputs libodbc.so are different or indicate different physical disk files, this problem exists. Both isql and psqlodbcw.so load libodbc.so. If different physical files are loaded, different ODBC libraries with the same function list conflict with each other in a visible domain. As a result, the database driver cannot be loaded.

  Solution:

  Uninstall the unnecessary unixODBC, such as libodbc.so.2, and create a soft link with the same name and the .so.2 suffix for the remaining libodbc.so.1 library.

• [unixODBC][Driver Manager]Invalid attribute value

  The unixODBC version may not be the recommended one. You are advised to run the odbcinst --version command to check the unixODBC version in the environment.

• authentication method 10 not supported.

  If this error occurs on an open-source client, the cause may be:

  The database stores only the SHA-256 hash of the password, but the open-source client supports only MD5 hashes.

  

  • The database stores the hashes of user passwords instead of actual passwords.
  • If a password is updated or a user is created, both types of hashes will be stored, compatible with open-source authentication protocols.
  • An MD5 hash can only be generated using the original password, but the password cannot be obtained by reversing its SHA-256 hash. Passwords in the old version will only have SHA-256 hashes and not support MD5 authentication.
  • The MD5 encryption algorithm has lower security and poses security risks. Therefore, you are advised to use a more secure encryption algorithm.

  To solve this problem, you can update the user password (see ALTER USER) or create a user (see CREATE USER) having the same permissions as the faulty user.

• unsupported frontend protocol 3.51: server supports 1.0 to 3.0

  The database version is too early or the database is an open-source database. Use the driver of the required version to connect to the database.

• isql: error while loading shared libraries: xxx

  The dynamic library does not exist in the environment. You need to install the corresponding library.